Governors Notes | EduRev

Theory of Machines (TOM)

Mechanical Engineering : Governors Notes | EduRev

The document Governors Notes | EduRev is a part of the Mechanical Engineering Course Theory of Machines (TOM).
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Introduction

  • The function of a governor is to regulate the mean speed of an engine, when there are variations in the load e.g. when the load on an engine increases, its speed decreases, therefore it becomes necessary to increase the supply of working fluid and governor ensures to supply this excess fuel to the engine, hence maintaining the mean speed.
  • The function of a governor is to maintain the speed of an engine within specified limits.

Types of Governors

Governors Notes | EduRev

  1. Watt Governor (Simple Conical Governor)
    (i) The simplest form of a centrifugal governor is Watt governor. It is basically a conical pendulum with links attached to a sleeve of negligible mass.
    Governors Notes | EduRev
    Schematic and Dynamics of Watt Governor
    2r x h = mg x r
    h = g/ω2 = 895/N2  (N is in rpm)
  2. Porter Governor
    (i) The Porter governor is a modification of the Watt’s governor, with central dead load attached to the sleeve.
    Governors Notes | EduRev
    Schematic and Dynamics of Porter Governor
    Governors Notes | EduRev
    Case 1: When β = θ → k = 1
    Governors Notes | EduRev
    Case 2: f = 0
    Governors Notes | EduRev
    Case 3: When β = θ & f = 0
    Governors Notes | EduRev
  3. Proell Governor
    (i) A Porter governor is known as a Proell governor if the two balls are fixed on the upward extensions of the lower links which are in the form of bent links BAE and CDF as shown in Figure.
    Governors Notes | EduRev
    Schematic and Dynamics of Proell governor
    Governors Notes | EduRev
    Special cases:
    Governors Notes | EduRev
  4. Hartnell Governor (Spring Controlled Governors)
    (i) It is a spring-controlled governor in which balls are mounted on the bell crank lever and sleeve is loaded by spring force as shown in Fig.
    (ii) Initially, the spring is fitted in compression so that a force is applied to the sleeve.
    (iii) Two bell-crank levers, each carrying a mass at one end and a roller at the other, are pivoted to a pair of arms which rotate with the spindle. The rollers fit into a groove in the sleeve.

Governors Notes | EduRevSchematic and Dynamic of Hartnell GovernorFs = spring force

Governors Notes | EduRev
Let s = stiffness of the spring
h1 = movement of the sleeve,
Governors Notes | EduRev
Governors Notes | EduRev

Governor Terminology

  1. Stability
    (i) A governor is said to be stable if with the increase in the speed, radius of rotation of balls increases.
    (ii) A stable governor brings the speed of the engine to the required value and there is not much hunting.      
  2. Sensitiveness of a Governor
    (i) A governor is said to be sensitive when there is larger displacement of the sleeve due to a fractional change in speed.
    (ii) Sensitiveness of the governor shall be defined as the ratio of speed range to the mean speed.
    Governors Notes | EduRev
  3. Isochronous Governor
    (i) A governor is said to be isochronous when the equilibrium speed is constant (i.e. range of speed is zero) for all radii of rotation of the balls within the working range, neglecting friction.
  4. Hunting
    (i) An excessive fast to & fro motion of the sleeve between the stoppers is known as hunting. It is the worst situation & will introduce noise and vibration.
    (ii) Hunting takes place in oversensitive governor.
    (iii) Higher the sensitiveness of the governor, the problem of hunting becomes more acute.

Controlling force

When the balls of a governor rotate in their circular path, the centrifugal force on each ball tends to move it outwards which is resisted by an equal and opposite force acting radially inwards and is known as the controlling force (CF).
Governors Notes | EduRevControlling force

Governors Notes | EduRevGraphical representation of various spring-controlled governors

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